Organic micropollutants in aerobic and anaerobic membrane bioreactors (MBR): changes in microbial communities and gene expression

The effect of organic micro-pollutants (OMPs) in wastewater on the microbial populations essential to the aerobic activated sludge and anaerobic digestion processes is not well understood. The purpose of this study was to examine the effect of OMPs on microbial population dynamics associated with both aerobic and anaerobic wastewater treatment. It was also desired to determine what OMPs show better biodegradability in aerobic compared to anaerobic membrane bioreactor (MBR) systems while monitoring biodegradation-related and antibiotic resistance-related gene expression levels in both reactors. To achieve this, two MBR systems (aerobic and anaerobic) were operated under the same conditions, treating wastewater spiked with a cocktail of 27 OMPs. Next-generation sequencing platforms were used to monitor changes in the microbial populations in the MBRs and their gene expression levels. Results show that spiking of OMPs in the wastewater feed had a clear effect on predominant and keystone bacterial populations in both MBRs while also significantly impacting gene expression levels associated with biodegradation. Finally, multiple antibiotic-type OMPs were found to have higher removal rates in the anaerobic MBR, while also ultimately impacting the presence of associated antibiotic resistance genes in both systems.